Patients with schizophrenia are compared to normal controls with respect to the uptake of the dopamine neurotransmitter-dependent tracer 6-18F- DOPA by positron emission tomography (PET). PET allows quantification and localization of tissue radionuclide content with high spatial resolution. 6-18F-DOPA, an analogue of L-DOPA allows in vivo visualization of dopamine and its metabolites in the areas of the brain believed to be involved in schizophrenia and Tourette's disorder. Patients are being studied on and off neuroleptics. The scans are analyzed by comparing regions of interest (ROI), and by utilizing metabolite analysis based on the Patlack model. To date, 14 normal controls and 26 schizophrenic patients (ten off and 16 on neuroleptics) have been studied. Preliminary data (12 normal controls, ten schizophrenic patients on neuroleptics and seven off) show a significant reduction in DOPA uptake in the basal ganglia structures of the group of patients off neuroleptics as compared to normal controls, and increased uptake in the group of patients on neuroleptics. In the cortical areas, decreased uptake in the anterior cingulate was noted in both the on and off schizophrenic patients compared to normal controls.